1. Field of the Invention
This invention relates to compression screw systems for applying compression to a fractured bone to aid in the healing thereof.
2. Description of the Prior Art
Compression screw systems, in general, consist of a lag screw for being anchored to the bone on one side of a fracture, a compression plate for being attached to the bone on the other side of the fracture, and a compression screw for extending from the compression plate to the lag screw to allow compression to be applied between the lag screw and the compression plate. The compression plate is usually adapted to fit over a portion of the lag screw to prevent the lag screw from rotating when the compression screw is screwed thereinto. More specifically, the lag screw is usually provided with a longitudinally directed keyway, and the compression plate is usually provided with a hollow barrel member for sliding over the lag screw, the barrel member being provided with a longitudinally directed key for co-acting with the longitudinally directed keyway of the lag screw to non-rotatably attach the lag screw and the compression plate together. However, this system is disadvantageous in that it is difficult and time consuming to fit the barrel member of the compression plate over the lag screw with the key of the barrel member properly engaging the keyway of the lag screw, especially since the end of the lag screw does not extend outward of the bone, but rather usually ends about one-half inch within the bone, thus requiring the surgeon to fit the two parts together in a trial-and-error type manner. Attempts have heretofore been made towards overcoming the above disadvantages and problems. For example, one attempt has been to screw an elongated extension member having a cross-section smaller than the cross-section of the lag screw into the end of the lag screw after the lag screw has been anchored to the bone to allow the surgeon to place the barrel member of the compression plate over the extension member and to merely slide the barrel member along the extension member to the lag screw. While this attempt does alleviate some of the disadvantages heretofore discussed, it does not completely overcome such problems since the surgeon must still fit the two pieces together in a substantially trial-and-error type method. Rather, this attempt merely serves to reduce the amount of trial-and-error in aligning the aperture of the barrel member with the outside of the lag screw. Another attempt has been to recess the key of the barrel member away from the forward end of the barrel member so as to take the necessary aligning steps into two distinct steps: first, aligning the aperture of the barrel member of the compression plate with the outside of the lag screw; next, aligning the key of the barrel member with the keyway of the lag screw. However, such an attempt does not entirely overcome the above problems and disadvantages since the surgeon must still fit the two parts together in substantially a trial-and-error type method.